JP-B-2-17080 discloses a technique on a direction finding machine for detecting the difference in phase between a reference signal and a direction signal of electric waves based on reception signals achieved by successively switching and sweeping an antenna group to carry out a direction measurement, and correcting a direction error caused by a signal delay of a reception circuit or the like by presetting a correction value into a counter which can be preset.
JP-A-8-98284 discloses a data reception device for detecting a reference pulse contained in received transmission data by utilizing the fact that the reference pulse concerned corresponds to the period of a transmission clock for encoding the transmission data, and measuring the pulse width of the reference pulse on the basis of a reference clock to generate a reception clock having the same communication speed as the transmission data. According to the data reception device, even when the pulse width of the reference pulse is not accurately equal to an integral multiple of the reference clock, and thus a phase lag of the reference pulse is gradually accumulated, a reception clock generator is reset in conformity with the variation point of the transmission data, that is, the bit boundary of the transmission data, so that the start of frequency-division of the reference clock is coincident with the variation point of the transmission data and the reception clock and the transmission data can be made coincident in phase with each other.
When the data reception mechanism disclosed in JP-A-8-98284 is used, a reception clock synchronous with the phase of transmission data can be generated, and even when a frequency lag exists between a reference clock used at the transmission side and a reference clock used at the reception side, the communications can be performed if the frequency lag is minute. However, when the frequency lag between these reference clocks is increased (for example, by about 2%), the accumulation error of the phase is rapidly increased with time lapse of the communication time, and thus the correction of the phase by using only the data reception mechanism cannot follow the rapid increase of the accumulation error, so that dropouts of bits may occur in the reception data. Therefore, in the conventional communication device, the reference clock is generated by using a high-precision and highly-stable quartz oscillation circuit.
The quartz oscillation circuit is more expensive than a ceramic oscillator, etc. Therefore, for the purpose of reducing the cost, it has been required to use a ceramic oscillation circuit or a CR oscillation circuit which is lower in precision, but has a larger effect in reduction of the cost.